Swift 3中的UIPinchGestureRecognizer

import UIKit

class ViewController: UIViewController {
    
    var pinchGesture: UIPinchGestureRecognizer!
    var initialTransform: CGAffineTransform = CGAffineTransform.identity
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        // 创建捏合手势识别器
        pinchGesture = UIPinchGestureRecognizer(target: self, action: #selector(handlePinch(_:)))
        view.addGestureRecognizer(pinchGesture)
    }
    
    @objc func handlePinch(_ gesture: UIPinchGestureRecognizer) {
        switch gesture.state {
        case .began:
            // 记录初始变换
            initialTransform = view.transform
        case .changed:
            // 应用缩放变换
            let newScale = gesture.scale * initialTransform.a
            view.transform = initialTransform.scaledBy(x: newScale, y: newScale)
        case .ended, .cancelled:
            // 手势结束，可以在这里处理一些收尾工作
            break
        default:
            break
        }
    }
}

view.layer.anchorPoint = CGPoint(x: 0.5, y: 0.5) // 设置缩放中心为视图中心